Inflatable bodies such as mattresses and cushions are used for a variety of purposes. In certain applications, especially in the medical fields, it is particularly desirable to modify the resiliency or Indentation Force Deflection (“IFD”) value of a mattress or a cushion over a given area. For example, and with respect to seating cushions, various portions of a user's anatomy require different levels of support. This recognition lead to the development of the invention disclosed in U.S. Pat. No. 5,282,286, which is incorporated herein by reference. Here, discrete resilient slabs of material are placed adjacent to one another within a single envelope or enclosure to provide different zones of IFD values. While achieving the objective of providing differentiated zones of IFD values within a single self-inflating seat cushion, the invention did not provide for modulating the cushion's internal air pressure for each or several zones.
Other attempts have been made in this respect. U.S. Pat. No. 6,463,610, for example, discloses a multi-chambered air bed that utilizes discrete tension members in the form of coils to provide mattress stability and prevent distension of the bed's outer sheets when internal pressure increases. The multiple chambers are created by establishing a septum or barrier within a larger sealed volume.
An alternative arrangement disclosing a composite structure is found in U.S. Pat. No. 6,651,277. In this invention, a self-inflating pad is combined with a means for receiving an auxiliary structure to modify the nature of the support. However, if unique zones of IFD values are desired, the modifications must be made to the auxiliary structure, which will either minimize the benefits of the self-inflating pad portion or result in sharp transition zones if the structure is not homogeneous.